The bird was found on Barnham Cross Common, near the fence line of the British Trust for Ornithology (BTO), in Thetford last Tuesday at 4pm with both breasts and head removed and skin and meat taken from the thighs.

A police spokesman said the animal had been cut cleanly, suggesting it had not been attacked by another animal.

The bird was found by a dog walker who reported the finding to the police and BTO.

PCSO Gavin Tampin, who was called to the incident, said he was struck by how “clean” the bird was.

“Normally when you see a bird that has been attacked by an animal there is blood everywhere but there was nothing.

“It seemed to be quite young, still a baby really.

“Whoever did it had obviously done similar before - it was like something you would get from the butchers,” he said.

A spokeswoman for the BTO said the bird had been ringed by one of its staff the previous year.

She added that while the poaching of fish and geese had been reported to the trust in the past, the killing of swans was rare.

Swans are protected under the 1981 Wildlife and Countryside Act, which makes it an offence to kill, injure or take wild birds, according to police.

Killing or injuring a swan carries a £5,000 fine or six months in jail. Stealing a swan egg is also an offence and carries the same maximum penalty.

Anyone with information is asked to call Thetford Police on 101 or Crimestoppers anonymously on 0800 555 111.